Fill missing dates in records

Question

I have a collection of ProductViews.

ProductView

{
    productId: \'5b8c0f3204a10228b00a1745,
    createdAt: \'2018-09-         


        

Answer 1

With some javascript and aggregation trick.

You need to first find the dates between the date range provided.

function getDates(startDate, stopDate) {
  var dateArray = []
  var currentDate = moment(startDate)
  var stopDate = moment(stopDate)
  while (currentDate <= stopDate) {
    dateArray.push(moment(currentDate).format('YYYY-MM-DD'))
    currentDate = moment(currentDate).add(1, 'days')
  }
  return dateArray
}

const dummyArray = getDates('2018-09-01', '2018-09-05')
dummyArray = [ "2018-09-01", "2018-09-02", "2018-09-03", "2018-09-04", "2018-09-05" ]

Now with the below aggregation you can find for the dates which are not available in the database.

db.collection.aggregate([
  { "$match": { productId } },
  { "$group": {
    "_id": { "$substr": ["$createdAt", 0, 10] },
    "count": { "$sum": 1 },
    "time": { "$avg": "$createdAt" },
  }},
  { "$sort": { "_id": 1 } },
  { "$project": { "date": "$_id", "views": "$count" }},
  { "$group": { "_id": null, "data": { "$push": "$$ROOT" }}},
  { "$project": {
    "data": {
      "$map": {
        "input": dummyArray,
        "in": {
          "k": "$$this",
          "v": { "$cond": [{ "$in": ["$$this", "$data.date" ] }, 1, 0 ] }
        }
      }
    }
  }},
  { "$unwind": "$data" },
  { "$group": { "_id": "$data.k", "count": { "$sum": "$data.v" }}}
])

and the output will be

[
    { date: '2018-09-01', views: 1 },
    { date: '2018-09-02', views: 3 },
    { date: '2018-09-03', views: 0 },
    { date: '2018-09-04', views: 2 },
    { date: '2018-09-05', views: 5 }
]